1. Field of the Invention
The invention relates to a dead-zone free magnetometer. More specifically, the invention relates to such a magnetometer including a gas cell, a multi-directional A.C. magnetic field H.sub.1 formed in said cell, and a plurality of circularly polarized resonance radiation rays travelling through said gas cell through said A.C. magnetic field H.sub.1, the direction of travel of at least one of said rays being different from the direction of travel of at least another one of said rays.
2. Description of Prior Art
Magnetometers, using a gas cell (also referred to as a vapour cell or an absorption cell), using gas cells, are known in the art as illustrated in, for example, RUBIDIUM VAPOUR MAGNETOMETER, L. W. Parsons and Z. M. Wiatr, Journal of Scientific Instruments, Vol. 39, pp. 292-300, June 1962; PRINCIPLES OF OPERATION OF THE RUBIDIUM VAPOR MAGNETOMETER, A. L. Bloom, Applied Optics, Vol. 1, page 61, January 1986; U.S. Pat. No. 4,600,886, Jensen, Jul. 15, 1986; U.S. Pat. No. 3,206,671, Colegrove, Jr. et al, Sep. 14, 1965, and U.S. Pat. No. 3,350,632, Robinson, Oct. 31, 1967. In the Parsons et al and Bloom references, the gas cells are filled with a vapour of an alkali metal. As in known magnetometers, D.sub.1 or D.sub.2 light from an alkali metal lamp is directed at the gas cell, and an alternating magnetic field H.sub.1 is formed in the gas cell. The light is directed at the gas cell through a circular polarizer, and the light rays travelling through the cell travel along a single direction, i.e., all of the rays are essentially parallel to each other. In a like manner, the A.C. magnetic field H.sub.1 formed in the gas cell is a unidirectional field.
The Colegrove, Jr. et al and Robinson patents teach magnetometers wherein the absorption cells are filled with a helium gas and the lamps are helium lamps.
Such known arrangements experience dead-zones i.e., at some orientation of the sensor with respect to the ambient magnetic field, the sensor does not generate a signal.
One solution to this problem has been to provide a mechanism for being adapted to continuously reposition the magnetometer so that such dead zones are avoided. Such a solution is illustrated in the Jenson patent above referred to. However, such solution requires sophisticated and expensive equipment for repositioning the magnetometer.